Predistortion linearizing

ABSTRACT

A method for a predistortion linearization of a branched signal for a RF amplifier, comprising supplying a branched signal to at least one input terminal ( 2 ); distributing power of the input signal present on at least one input terminal ( 2 ) to a plurality of parallel branch-circuits ( 16, 18, 20 ) as a branched signals by a power distributing circuit ( 4 ); controlling a phase parameter and an amplitude parameter of the branched signals by at least one nonlinear branch-circuit ( 18, 20 ); controlling a phase parameter and an amplitude parameter of the branched signals by at least one linear branch-circuit ( 16 ); combining output branched signals of at least one nonlinear branch circuit ( 18, 20 ) with the output branched signals of at least one linear branch circuit ( 16 ) by a power combining circuit ( 12 ); providing an output branched signal of the power combining circuit ( 12 ) on at least one output terminal ( 14 ). Furthermore, a circuit for a predistortion unit linearizing a signal for a RF amplifier and a layout of a predistortion linearization of a signal for a RF amplifier are disclosed.

The present invention relates to a predistortion linearization, inparticular to a method, and an electronic device comprising a circuitfor a predistortion linearization.

U.S. Pat. No. 5,523,716 discloses a predistortion linearizer and amethod for distorting an AC input branched signal to a power amplifierproviding a distortion to the input branched signal which iscomplementary to a distortion in terms of gain and phase, introduced bythe power amplifier as a function of the branched signal amplitude,thereby to linearize the power amplifier. The linearizer includes aswitching circuit having an input terminal and an output terminal and apair of anti-parallel diodes connected between the input terminal andthe output terminal of the switching circuit The linearizer also has animpedance circuit comprising solely passive electrical elementsconnected between the input terminal and the output terminal of theswitching circuit, wherein elements of the impedance circuit have valuesselected to introduce the complementary distortion to the input branchedsignal as a function of the amplitude of the input branched signal tolinearize the power amplifier.

U.S. Pat. No. 5,703,530 describes a radio-frequency amplifier circuit ofsimple construction having low power consumption and low heat generationand amplifying an input branched signal while maintaining compositetriple beat (CTB) distortion, type cross modulation distortion, at aminimum. The radio-frequency amplifier comprises a transformer whichtransforms an input branched signal from an unbalanced state to abalanced state. The amplifier further comprises at least one distortiongeneration circuit including a first circuit having a nonlinear elementand a first delay line coupled in series, and a second circuit having anattenuation element and a second delay line coupled in series. The firstand second circuits are coupled in parallel. At least one distortiongeneration circuit is coupled to an input, an output and/or an functionpoint of a radio-frequency amplification stage of the radio-frequencyamplifier. The first and second delay lines are configured to create adelay time change in a branched signal input level of a branched signalinput to the radio-frequency amplification stage which opposes a delaytime change in the branched signal input level caused by a delay timedifference between the input and output of the radio-frequencyamplification stage. A transformer transforms the amplified inputbranched signal from the balanced state back to an unbalanced statebefore outputting the amplified branched signal from the amplifiercircuit.

U.S. Pat. No. 5,798,854 discloses an electronic circuit providing alinear output from a nonlinear transmission device such as a laser.Second and higher order distortion of the nonlinear device iscompensated by applying a predistorted branched signal equal inmagnitude and opposite in sign to the real and imaginary components ofdistortion produced by the nonlinear device. The input branched signalfor the nonlinear device is applied to an in-line electrical pathcoupled to the nonlinear device. The in-line path contains at least onecomponent for generating primarily real components of distortion. Insome applications, at least one component for generating imaginarycomponents of distortion is located on the in-line path. Filter stagesare used to provide frequency dependent predistortion. In a preferredembodiment, an attenuator, an MMIC amplifier, a CATV hybrid amplifier,and a varactor in line with a semiconductor laser, provide thepredistorted branched signal. In another embodiment, the real componentof predistortion is generated by a FET configured as a voltagecontrolled resistor. In still another embodiment, the real component ofpredistortion is generated by the parallel combination of a diode and aresistor connected in series with the RF branched signal path. Alsoprovided is a separate circuit including anti-parallel diodes andreactive elements for generating frequency dependent third-orderpredistortion.

U.S. Pat. No. 5,966,049 discloses a broadband linearizer for use with apower amplifier. The broadband linearizer includes a broadbandlinearizer bridge, a preamplifier/attenuator, a postamplifier/attenuator, and a control circuit. The broadband linearizerbridge includes a power divider and a power combiner interconnected bylinear and nonlinear arms. The linear arm has a phase shifter, a passiveequalizer, and a first delay line that are serially coupled together.The nonlinear arm has a distortion generator, an attenuator and a seconddelay line that are serially coupled together. 91˜hc control circuitcontrols respective settings of the broadband linearizer bridge,preamplifier/attenuator and post amplifier/attenuator. The controlcircuit provides bias circuitry and sends command and telemetry branchedsignals to control operation of the broadband linearizer. The broadbandlinearizer provides for independent, flexible gain and phase controlthat can match with different kinds of power amplifiers having variedgain and phase performance.

U.S. Pat. No. 6,018,266 describes a radio-frequency system including areflective diode linearizer. The reflective diode linearizer has aquadrature hybrid circuit with an input, an output, a first tuned port,and a second tuned port. Each of the tuned ports has a reflectioncircuit in electrical communication. Each reflection circuit includes afirst Schottky diode having a cathode in electrical communication withthe tuned port, a second Schottky diode having an anode in electricalcommunication with the tuned port, a first delay line having a first endin electrical communication with the tuned port, a second delay linehaving a first end in electrical communication with an anode of thefirst Schottky diode and also in electrical communication with a cathodeof the second Schottky diode, and a radio-frequency resistive elementhaving a first end in electrical communication with a second end of thefirst delay line and a second end in electrical communication with asecond end of the second delay line and with an electrical ground.

U.S. Pat. No. 5,523,716, U.S. Pat. No. 5,703,530, U.S. Pat. No.5,798,854, and U.S. Pat. No. 5,966,049 suggest means for amplitudeadjustment of the branched signal incident on the input terminal of adistortion circuit and means for amplitude adjustment of the branchedsignal output by an output terminal of the distortion circuit. Thesolutions of these patents make use of two main elements: conventional,single-ended or push-pull type, amplifiers; and distortion generationcircuit made of two parallel branch-circuits including time delay andpower dissipating components one of which is a nonlinear impedancebranch-circuit with nonlinear device and another is usually a linearpassive branch-circuit. The distortion generator circuits have severaldisadvantages, when used. They do not provide the isolation betweenbranch-circuits so the tuning of one of the branch-circuits is effectingthe performance/delay time, impedance and transmission parameters/ofothers parallel branch-circuits. They do not provide the required rateof gain/phase expansion or AM/AM/AM/PM in case of deep saturation of oneamplification stage or required characteristic of AM/AM and AM/PM vs.input/output power in case of a multistage amplifier. Furthermore, theyshow high RF branched signal losses (more than −15 dB), to achieve therequired higher AM/PM and AM/AM regulation rate.

U.S. Pat. No. 6,018,266 describes a predistortion circuit where the keyelements are the hybrid and diodes and where the main principle is areflection of the branched signal from the diodes, connected to thehybrid ports, where the branched signal is going through the hybrid fromthe input port to the diodes and then reflected back to the other hybridoutput port.

It is an object of the present invention to provide a method, and anelectronic device comprising a circuit for a predistortionlinearization.

To achieve the object of the present invention, a method for apredistortion linearization of a branched signal for a RF amplifier isdisclosed, comprising supplying an input signal to at least one inputterminal; distributing the input signal present on at least one inputterminal to a plurality of parallel branch-circuits as branched signalsby a power distributing circuit; controlling a phase parameter and/or anamplitude parameter of the branched signals by at least one nonlinearbranch-circuit; controlling a phase parameter and/or an amplitudeparameter of the branched signals by at least one linear branch-circuit;combining output signals of at least one nonlinear branch circuit withthe output signals of at least one linear branch by a power combiningcircuit; providing a final output signal of the predistortion unit fromthe power combining circuit on at least one output terminal. The methodof the present invention increases the AM/AM and AM/PM expansion rate.That is enabled by using parallel branches of linear and nonlinearbranches, wherein the parallel branches comprise an amplificationelement. The AM/AM rate and the AM/PM rate are separately controlled.

According to a preferred embodiment of the invention, the controlling ofa phase parameter and/or an amplitude parameter of a branched signal byat least one nonlinear branch-circuit comprises controlling a phase of abranched signal by at least one phase control unit and/or; controllingan amplitude of a branched signal by at least one linear amplitudecontrol unit and/or; controlling an amplitude of a branched signal by atleast one nonlinear amplitude control unit. The AM/AM rate is controlledby the nonlinear branch. This provides the possibility of controllingthe AM/AM rate separately from the AM/PM rate.

According to a preferred embodiment of the invention, the controlling ofa phase parameter and/or an amplitude parameter of a branched signal byat least one linear branch-circuit comprises controlling a phasevariation of a branched signal by at least one phase control unitand/or; controlling an amplitude of a branched signal by at least onelinear amplitude control unit. The linear branch controls the AM/PM rateseparately from the AM/AM rate.

According to a preferred embodiment of the invention, the linear and/orthe nonlinear amplitude control unit is controlled depending on a powerlevel of an input signal. This advantageous feature allows that eachbranch starts with the regulation of its parameter depending on a powerlevel of the input signal. This provides the possibility of each branchbeing adapted to a special power level of the input signal.

According to a preferred embodiment of the invention, the linear and/orthe nonlinear amplitude control unit are controlled depending on anexternal adjustable value. This advantageous feature makes it possibleto adjust a value, from which the regulation of each branch depends.

According to a preferred embodiment of the invention, the linear and/orthe nonlinear branch-circuit has its own specific RF power level fromwhich its predistortion of amplitude and/or phase starts, which isdefined by an individual nonlinear function.

To achieve the object of the present invention, a method for apredistortion linearization is disclosed, where the elements such as avaricap and a gain controlled amplifier can be used in particular forAM/AM and AM/PM temperature compensation of a linearized power module,comprising supplying an input signal to at least one input terminal;distributing the input signal present on at least one input terminal toa plurality of parallel branch-circuits as branched signals by a powerdistributing circuit; controlling a phase parameter and/or an amplitudeparameter of the branched signals by at least one nonlinearbranch-circuit; controlling a phase parameter and/or an amplitudeparameter of the branched signals by at least one linear branch-circuit;combining output signals of at least one nonlinear branch circuit withthe output signals of at least one linear branch by a power combiningcircuit; providing a final output signal of the predistortion unit fromthe power combining circuit on at least one output terminal.

To achieve the object of the present invention, an electronic devicecomprising a circuit for a predistortion unit linearizing a signal for aRF amplifier are disclosed, comprising at least one input terminal; apower distributing circuit distributing an input signal present on atleast one input terminal to a plurality of parallel branch-circuits asbranched signals; at least one nonlinear branch-circuit controlling aphase parameter and/or an amplitude parameter of the branched signals;at least one linear branch-circuit controlling a phase parameter and/oran amplitude parameter of the branched signals; a power combiningcircuit combining output signals of at least one nonlinear branchcircuit with the output signals of at least one linear branch circuit;at least one output terminal providing an output signal of thepredistortion unit from the power combining circuit. The advantageousfeature of the circuit and the layout is that the present inventioncancels more than 20 dB of the third-order inter-modulation. Minimizingthe third-order inter-modulation is very important for wirelesscommunication systems with digital modulation, such as WCDMA and EDGE.The circuit is very suitable for use in combination with a multistagepower amplifier. The circuit can be used for a wide variety of poweramplifiers, due to almost independent adjustability of AM/AM and AM/PMregulation rates and threshold power level. The circuit can be embodiedin a semiconductor device, or as a circuit on a carrier such as aprinted circuit board. The electronic device is preferably a modulecomprising a power amplifier and the circuit. Such module can forinstance be used in portable communication devices, such as a mobilephone.

According to a preferred embodiment of the invention, the nonlinearbranch-circuit comprises at least one phase control unit controlling thephase of a branched signal and/or; at least one linear amplitude controlunit controlling the amplitude of a branched signal and/or; at least onenonlinear amplitude control unit controlling the amplitude of a branchedsignal. The advantageous feature of the one linear branch circuit isthat the AM/AM rate is regulated separately from the AM/PM rate.

According to a preferred embodiment of the invention, the linearbranch-circuit comprises at least one phase control unit controlling thephase of a branched signal and/or; at least one linear amplitude controlunit controlling the amplitude of a branched signal.

According to a preferred embodiment of the invention, the nonlinearamplitude control unit comprises at least one nonlinear element; and atleast one amplifier.

According to another embodiment, the power combining circuit comprises afeedback. This feedback is present between the output and the input ofthe amplifier in the power combining circuit. Particularly, it is adouble negative feedback, including a voltage feedback and a currentfeedback. In addition, each of the branches is provided with an outputimpedance. Such output impedance is advantageously embodied withresistors, which for instance an resistance between 10 and 100 Ohm. Dueto this feedback the input impedance of the combining circuit can berelatively low.

The advantage of this embodiment is that its enables a modular approach.The embodiment provides a good isolation between the branches. Therewitha branch can be modified without having the influence thereof in theother branches. Alternatively parallel branches may be added or removed.This enables modification of the concept for different applications.Basically the circuit is suitable for all applications at highfrequencies, that need a good linearity and a high power level. Thepredistortion circuitry may give a correction of about 3 dB peramplifier stage, and more than one predistortion circuit can be appliedin a mulistage amplifier.

More precisely, the power amplifier characteristics in a saturationregion have rather non-linear behaviour and are more or less unique fora specific amplifier. The amplifier is therein dependent on the usedpower transistors, the matching technique and the quantity of amplifierstages. The predistor characteristics—i.e. the AM/AM and AM/PMcharacistics—should thus be fitted for each individual case.Conventional power combining circuits such as Hybrid, Wilkinson, Langeand ratrace couplers, usually require a large area and have nonethelessa limited frequency band. Alternative combining circuits are implementedwith lumped elements, but also these have the disadvantage of a largearea. Additionally, many lumped elements are needed and thisimplementation is not very suitable for IC design.

These drawbacks are solved by the use of an amplification technique withfeedback and particularly with double negative feedback. As advantagescan be mentioned that the control of gain and input impedance is easy;that it results in a high linearity or in other words that theintermodulation distortion is adequately compensated; that it has a goodtemperature stability and that it is applicable for wide bands.Moreover, is the embodiment easily implementable in IC design and isonly a limited surface area required. The advantageous feature of thelinear branch circuit is that the AM/PM rate is regulated separatelyfrom the AM/AM rate.

According to a preferred embodiment of the invention, the nonlinearelement is a diode.

According to a preferred embodiment of the invention, the nonlinearelement is a circuit of anti-parallel connected diodes.

According to a preferred embodiment of the invention, a control backwardbiasing unit is connected to the circuit of anti-parallel connecteddiodes.

According to a preferred embodiment of the invention, the nonlinearelement is a transistor.

According to a preferred embodiment of the invention, the amplifier is again control amplifier.

According to a preferred embodiment of the invention, the amplifier hasits own amplifier class.

According to a preferred embodiment of the invention, the amplifier isan A- or AB- or B- or C- or E- or F-class amplifier.

According to a preferred embodiment of the invention, the linearamplitude control unit is a gain control amplifier and/or an attenuatorand/or a resistor and/or a dissipative transmission line and/or acontrollable resistive component.

According to a preferred embodiment of the invention, the amplifier hasits own amplifier class.

According to a preferred embodiment of the invention, the amplifier isan A- or AB- or C- or E- or F-class amplifier.

According to a preferred embodiment of the invention, the amplifiercomprises at least one transistor.

According to a preferred embodiment of the invention, the phase controlunit comprises at least one transmission line.

According to a preferred embodiment of the invention, the transmissionlines are connected in parallel and/or in series.

According to a preferred embodiment of the invention, the transmissionline is a quarter-wavelength transmission line.

According to a preferred embodiment of the invention, the transmissionline is artificial and/or distributed.

According to a preferred embodiment of the invention, the transmissionline is an impedance transformation circuit and/or a filtering circuitand/or a phase shifter circuit.

According to a preferred embodiment of the invention, the transmissionline comprises a serial and/or a parallel circuit of at least oneresistor and/or capacitance and/or inductance.

According to a preferred embodiment of the invention, the phase controlunit comprises at least one controlled resistive element.

According to a preferred embodiment of the invention, the controlledresistive element is connected between ground and a connection point ofat least two transmission lines.

According to a preferred embodiment of the invention, the controlledresistive element is connected between ground and at least one terminalof the amplifier of the linear amplitude control unit and/or thenonlinear amplitude control unit.

According to a preferred embodiment of the invention, a control input ofthe controlled resistive element is connected to at least one terminalof the amplifier of the linear amplitude control unit and/or thenonlinear amplitude control unit.

According to a preferred embodiment of the invention, the linear and/orthe nonlinear branch-circuit has a filtering circuit at an outputterminal.

According to a preferred embodiment of the invention, the filteringcircuit is a low-pass filter or a high-pass filter.

According to a preferred embodiment of the invention, the filteringcircuit comprises a serial and/or a parallel circuit of at least oneresistor and/or at least one capacitance and/or at least one inductance.

According to a preferred embodiment of the invention, the circuit isintegrated in a semiconductor circuit.

According to a preferred embodiment of the invention, the circuit isimplemented in MMIC circuit technology.

These and various other advantages and novelty features whichcharacterize the present invention are pointed out with particularity inthe claims annexed hereto and forming part hereof. However, for a betterunderstanding of the invention, its advantages, and the object achievedby its use, reference should be made to the drawings which form afurther part hereof, and to the accompanying descriptive matter in whichpreferred embodiments of the present invention are illustrated anddescribed.

In the drawings:

FIG. 1 shows a basic block diagram of the predistortion linearizer ofthe present invention;

FIGS. 2 to 6 show a circuit diagram and graphs of an embodiment of thepresent invention;

FIGS. 7 to 16 show another embodiment of the present invention with therelated circuit diagrams and the related measured graphs;

FIGS. 17 to 28 show different embodiments of the present invention.

FIG. 1 shows a basic block diagram of the present invention of apredistortion linearizer. Equivalent parts have equivalent numbers. Thisis done in the whole description of the present invention. The basicblock diagram of FIG. 1 comprises an input terminal 2 connected to apower distribution circuit 4. The power distribution circuit 4 isconnected to the parallel branches 16, 18 and 20. Branch 16 representsthe first linear branch, branch 18 represents the first nonlinearbranch, and branch 20 represents the n^(th) nonlinear branch. The branch16 comprises a phase control unit 6, also called transmission line unit,connected on one side to the power distribution circuit 4 and on theother side to a linear amplitude control unit 8. The linear amplitudecontrol unit 8 is connected on the other side to another phase controlunit 6. The phase control unit 6 is connected on the other side to apower combiner circuit 12.

The branch 18 is connected in parallel to the branch 16 between thepower distribution circuit 4 and the power combiner circuit 12. Thebranch 18 comprises a serial circuit of a nonlinear amplitude controlunit 10 connected on the one side to the power distribution circuit 4and on the other side to a linear amplitude control unit 8. The linearamplitude control unit 8 is connected on the other side to phase controlunit 6. The phase control unit 6 connected on the other side to thepower combiner circuit 12.

The branch 20 is the n^(th)-branch of this block diagram. The branch 20is connected in parallel to the branches 16 and 18 between the powerdistribution circuit 4 and the power combiner circuit 12. The branch 20comprises a serial circuit comprising a nonlinear amplitude control unit10 connected on the one side to the power distribution circuit 4 and onthe other side to a linear amplitude control unit 8. The linearamplitude control unit 8 is connected on the other side to a phasecontrol unit 6. The phase control unit 6 is connected on the other sideto the power combiner circuit 12. The power combiner circuit 12 isconnected to the output terminal 14.

The predistortion unit of the embodiments of the invention includeseveral parallel branches which generate a predistortion signal atdifferent levels of input power, while providing also a differentpredistortion rate which provides a better compensation of graduallychanging rate of AM/AM and AM/PM in the power amplifier.

FIG. 2 shows a possible embodiment of the present invention. Theembodiment comprises an input terminal 30 connected to the capacitances32 and 68. The other side of the capacitance 32 is connected to an anodeof diode 34 and to a cathode of diode 38. The cathode of diode 34 isconnected to a resistor 44, a resistor 46 and a capacitance 36. Theother side of resistor 44 is connected to terminal 42. The anode ofdiode 38 is connected to the other side of resistor 46, to a capacitance40, and to a resistor 48. The other side of the resistor 48 is connectedto ground. The other side of the capacitance 40 is connected to theother side of capacitance 36 and to a resistor 50, a base terminal oftransistor 62, a resistor 52 and a capacitance 54. The other side of theresistor 52 is connected to terminal 60. The other side of resistor 50is connected to ground. The other side of the capacitance 54 isconnected to a resistor 56. The other side of the resistor 56 isconnected to a resistor 58 and a collector terminal of transistor 62.The other side of the resistance 58 is connected to terminal 60. Thecollector terminal of transistor 62 is connected to the resistors 56, 58and a capacitance 64.

An emitter of the transistor 62 is connected to an adjustable resistor66. The other side of the resistor 66 is connected to ground. The otherside of the capacitance 64 is connected to an output terminal 88. Theother side of the capacitance 68 is connected to a delay line 70, whichis adjustable. The other side of the delay line 70 is connected to aresistor 74, a resistor 72, a capacitance 76, and a base terminal oftransistor 84. The other side of the resistor 74 is connected to ground.The other side of the resistor 72 is connected to a terminal 80. Theother side of the capacitance 76 is connected to a resistor 78. Theother side of the resistor 78 is connected to a resistor 82, acapacitance 90, and a collector terminal of the transistor 84. The otherside of the capacitance 90 is connected to the output terminal 88. Theemitter terminal of the transistor 84 is connected to a resistor 86. Theother side of the resistor 86 is connected to ground.

This embodiment comprises only two branches for simplicity. There are anonlinear branch and a linear branch. The nonlinear branch is the upperbranch shown in FIG. 2 with a threshold regulation circuit comprisingthe elements 34 to 48 and an amplifier stage comprising the elements 50to 66. The linear branch comprises a delay line 70 of any type and alinear amplifier stage comprising the elements 72 to 86.

The amplifier stage of the transistor 62 provides the gain, whichcompensates the signal losses in the threshold control circuit, which iscreated by the diodes 34 and 38. The gain of the amplifier stage isdefined by the values of the feedback resistors 56 and 66 and mayachieve an attenuation value of (1 . . . 10)dB. When tuning the value ofthe resistor 66 in the emitter of transistor 62 from 0 to 4 Ohm, thegain of the amplifier stage varies from 4 to 10 dB, providing an almostindependent AM/AM rate regulation, where the AM/PM rate is constantrelative to the resistor 66, which is shown in the FIGS. 3 and 4.

The amplifier stage in the linear branch has lower gain and isadvantageous for providing good isolation of the delay line from thenonlinear branch and regulation of the initial value of the transmissioncoefficient of the predistortion unit of this embodiment.

Providing additional nonlinear parallel branches, the required AM/AM andAM/PM characteristic shapes can be achieved in this embodiment withoutdegrading of the original parameters, due to the properties of theamplifiers to isolate the output of every branch from others, providedthat the parameter S12 of the amplifier is less than −10 dB.

In summary, the specific embodiment of the present invention describedabove comprises a linear branch and at least one nonlinear branch, whichis connected in parallel to the linear branch. The nonlinear branchcomprises an amplifier stage of an amplifier in A-class and a thresholdpower control unit with independent biasing. The nonlinear branchcontrols the AM/AM rate. The linear branch also comprises an amplifierstage and a control unit with controlled bias in the linear branch. Thecontrol unit, for example a delay line, controls the AM/PM rate. Theamplifier stage comprises an A-class amplifier. The linear branchcontrols the AM/PM rate.

In the embodiment of the present invention described above, there is anamplification element inside the parallel branches which in factradically increases the AM/AM and AM/PM expansion rate and provides theisolation between said parallel branch outputs when combined, whichhelps for independent tuning and adjustment of said parallel branchparameters.

The embodiment of the present invention described above also gives asolution for control of the threshold power level, such as anti-paralleldiodes with independent biasing, whereby in this embodiment terminal 42and an A-class amplifier, or a B-/C-class amplifier with controlled biasin one independent nonlinear branch, the threshold level, the inputpower level, above which the amplitude and phase transfercharacteristics of the predistortion unit start to be changed, can beadjusted by one control signal through one special port.

In the embodiment shown in FIG. 2 the AM/AM rate is controlled by theadjustable resistor 66 and the AM/PM rate is controlled by theadjustable delay line 70. FIGS. 3 and 4 show measured lines atindependent AM/AM regulation at constant AM/PM rate in the predistortionunit embodiment of FIG. 1. The curve show different values of theresistor 66. The curve 100 represents the value of 0 Ohm of the resistor66. The curve 102 represents the value of 1 Ohm of the resistor 66. Thecurve 104 represents the value of 2 Ohm of the resistor 66. The curve106 represents the value of 3 Ohms of the resistor 66. The curve 108represents the value of 4 Ohms of the resistor 66.

FIGS. 5 and 6 show independent AM/PM regulation at constant AM/AM ratein the predistortion unit embodiment of FIG. 2. In FIG. 5 the curve 110represents 30°. The curve 112 represents 40°. The curve 114 represents50°. The curve 116 represents 60°. The curve 118 represents 80°. Thecurve 120 represents 90°. In FIG. 6, the curve 122 represents 30°. Thecurve 124 represents 40°. The curve 126 represents 50°. The curve 128represents 60°. The curve 130 represents 70°. The curve 132 represents800.

FIG. 7 shows another embodiment of the present invention. The embodimentshown comprises an input terminal 140 connected to a capacitance 142.The capacitance 142 is connected on the other side to the anode of adiode 158, the cathode of a diode 160 and a capacitance 144. Thecapacitance 144 is connected on the other side to a delay line 146. Thedelay line 146 is connected on the other side to a resistor 148. Theresistor 148 is connected on the other side to a capacitance 150 and aresistor 152. The capacitance 150 is connected on the other side toground. The resistor 152 is connected on the other side to an outputterminal 172. The cathode of the diode 158 is connected to an inductance156, a capacitance 166 and a resistor 162. The other side of theresistor 162 is connected to the anode of the diode 160, an inductance164 and a capacitance 168. The inductance 164 is connected to ground.The other side of the capacitance 168 is connected to another side ofthe capacitance 166 and an amplifier 170. The amplifier 170 is connectedto the output terminal 172. The terminal 154 of the threshold powercontrol is connected to the other side of the inductance 156.

The amplifier 170 is a gain control amplifier. The capacitance 150 is avariable capacitance or an element with a controlled capacitance value.The embodiment is a predistortion unit with extended dynamic range andcontrollable AM/AM and AM/PM regulation rates. It has been shown thatthe amplifier 170, when gain varies from 0 dB to 6 dB, simultaneouslyprovides phase valuation rate control from 5′/dB to 20′/dB and anamplitude regulation rate control from 0.3 dB/dB to 1 dB/dB.Furthermore, the variation of the capacitance 150 from 0 to 3 pF canprovide AM/AM regulation rate control, while the AM/PM ratecharacteristic is constant. The IRL of the predistortion unit is lessthan −10 dB in the power range. The initial losses also can be improvedto about −3 dB instead of 8.6) dB.

The predistortion unit of the embodiments of the present inventionprovides an extended dynamic range, a control over a threshold inputpower level at which the amplitude and phase regulation begins, anindependent control over amplitude and phase regulation rates in therange of a predistortion, and a higher amplitude and phase regulationrate.

This predistortion unit can also be used at the same time fortemperature compensation of linearized power module, where a VARICAP,presented as a capacitance 150, is a controlled element of an AM/AMcompensation loop and an amplifier control element for an AM/PMcompensation.

The FIGS. 8 to 16 show different measurements of the embodiment of FIG.7. FIGS. 8, 9 and 10 represent AM/AM and AM/PM and IRL versus differentbias voltage values. FIGS. 11 and 12 show AM/AM and AM/PM regulationrate of the predistortion unit versus different values of thecapacitance 150. FIG. 13 shows the effect of the different values of thecapacitance 150 on IRL of the predistortion unit of FIG. 7. FIGS. 14 and15 show the AM/AM and the AM/PM regulation rate of the predistortionunit versus the gain of the amplifier. FIG. 16 shows the effect of theamplifier gain on IRL of the predistortion unit.

Further embodiments of the present invention are presented in FIGS. 17to 27. In order to show the principle and for reasons of simplicity,only the first and second branches are shown.

FIG. 17 shows an embodiment of the present invention. The embodimentcomprises an input terminal 180 connected to a capacitance 182 and to acapacitance 202. The other side of the capacitance 182 is connected toan anode of the diode 184 and to a cathode of the diode 188. The cathodeof the diode 184 is connected to a capacitance 186, a resistor 194 and aresistor 196. The resistor 194 is connected on the other side to aterminal 192. The capacitance 186 is connected on the other side to aninput terminal of an amplifier 200 and a capacitance 190. The other sideof the resistor 196 is connected to the other side of the capacitance190, a resistor 198 and the anode of the diode 188. The other side ofthe resistor 198 is connected to ground. The amplifier 200 is connectedto a gain control unit 201. The upper terminal of the amplifier 200 isconnected to the output terminal 212. The other side of the capacitance202 is connected to a delay line 204. The other side of the delay line204 is connected to a resistor 206. The other side of the resistor 206is connected to an adjustable capacitance 208 and to a resistor 210. Theother side of the capacitance 208 is connected to ground. The other sideof the resistor 210 is connected to the output terminal 212.

The embodiment described includes an amplification block (so-called gaincontrol amplifier-AGC) which helps for low losses of the predistortionunit and higher achievable rates of the phase and amplitudepredistortions.

The elements 184 to 198 provide a threshold control of the input signal.The terminal 192 provides the bias voltage of the threshold controlunit. Furthermore, the threshold control unit of the elements 184 to 198and the amplifier 200 form the nonlinear branch. The linear branch isformed by the delay line 204 and the resistors 206 and 210 and theadjustable capacitance 208. The adjustable capacitance 208 serves tocontrol the AM/PM rate.

FIG. 18 shows another embodiment of the present invention. Theembodiment comprises an input terminal 214 connected to a capacitance216 and to a capacitance 238. The capacitance 216 is connected on theother side to a threshold control unit, which is equivalent to thethreshold control unit of FIG. 17 described earlier. Therefore, theelements 218 to 232 are equivalent to the elements 184 to 198 of FIG.17. The capacitances 220 and 224 are connected to a delay line 234. Thedelay line is connected on the other side to an amplifier 236 which is again control amplifier. The output of the amplifier 236 is connected tothe output terminal 246. The other side of the capacitance 238 isconnected to a resistor 240. The other side of the resistor 240 isconnected to an input terminal of an amplifier 242. The amplifier 242 isalso a gain control amplifier.

The output terminal of the amplifier 242 is connected to a delay line244. The output of the delay line 244 is connected to the outputterminal 246. In this embodiment both branches have a gain controlamplifier. These gain control amplifiers 236 and 242 can provideseparate amplitude and phase predistortion rate adjustment without gainlosses. The upper branch of FIG. 18 is the nonlinear branch providingthe AM/AM rate regulation, and the lower branch of FIG. 18 provides theAM/PM rate regulation.

FIG. 19 shows another embodiment of the present invention. Thisembodiment comprises an input terminal 250 connected to a capacitance252 and to a capacitance 262. The other side of the capacitance 252 isconnected to a resistor 254. The other side of the resistor 254 isconnected to a delay line 256. The other side of the delay line 256 isconnected to an amplifier 258. The amplifier 258 is a B-class amplifier.The amplifier 258 is connected to a bias control unit 260. The outputterminal of the amplifier 258 is connected to an output terminal 270.The other side of the capacitance 262 is connected to a resistor 264.The other side of the resistor 264 is connected to an amplifier 266. Theamplifier 266 is a gain control amplifier. The output terminal of theamplifier 266 is connected to a delay line 268. The other side of thedelay line is connected to the output terminal 270.

The embodiment shown has the following features. The delay lines 256 and268 specify the predistortion rate for the required phase. The gain ofthe amplifier 266 defines the predistortion unit gain. The amplifier 258connected to the bias control unit 260 defines a threshold power leveladjustment. An amplitude predistortion rate is defined by the ratiobetween re-gain of the amplifier 266 and the gain of the amplifier 258.The resistors 254 and 264 are used for power division and matchingconditions.

The embodiment of FIG. 20 comprises an input terminal 272 connected to apower divider 274. The power divider 274 is connected on one side to adelay line 276 and to an input terminal of an amplifier 280 on the otherside. The amplifier 280 is a gain control amplifier. The other side ofthe delay line 276 is connected to an input terminal of an amplifier278. The amplifier 278 is a B-class amplifier. The amplifier 278 isconnected to a bias control unit which is not shown. The output of theamplifier 278 is connected to an output terminal 284. The outputterminal of the amplifier 280 is connected to one side of a delay line282. The other side of the delay line 282 is connected to the outputterminal 284.

The difference between the embodiment shown in FIG. 20 and the formerembodiments is that that the embodiment of FIG. 20 comprises a powerdivider 274 at the input. This power divider 274 can provide better andconstant input return losses.

The embodiment of FIG. 21 comprises an input terminal 290 connected to ahybrid coupler 294. A 50-OHM resistor 292 is connected on the one sideto the hybrid coupler 294. The other side of the resistor 292 isconnected to ground. The hybrid coupler 294 crosses the lines from theresistor 292 to an A-class amplifier 298 with the line of the inputterminal 290 to an amplifier 296. Therefore, the input terminal 290 isconnected directly via the hybrid coupler 294 to the amplifier 296. Alsothe resistor 292 is connected directly via the hybrid coupler 294 to aninput terminal of the amplifier 298. The amplifier 298 is a gain controlamplifier. The output terminal of the amplifier 298 is connected to oneside of a delay line 300. The delay line 300 is adjustable. The otherside of the delay line 300 is connected to an output terminal 302. Theamplifier 296 is a B-class amplifier connected to a bias control unit.The output terminal of the amplifier 296 is connected to the outputterminal 302.

Just like the embodiment shown in FIG. 20, the embodiment of FIG. 21also differs from the preceding embodiments in that the embodiment ofFIG. 21 comprises a power divider at the predistortion unit input. Thispower divider in FIG. 21 is represented by the hybrid coupler 294. Thishybrid coupler 294 provides better and constant input return losses.

FIG. 22 shows an embodiment of the present invention comprising an inputterminal connected to a power divider 314. A resistor 312 is connectedon one side to ground and on the other side the resistor is connected tothe power divider 314. The power divider 314 crosses the lines from theinput terminal 310 to a 90° delay line 324 with the line from theresistor 312 to a delay line 316. The delay line 316 is connected on theother side to a gate terminal of a transistor 318. The transistor 318 isa B-class amplifier. The drain terminal of transistor 318 is connectedto a power supply which is not shown. The drain terminal of transistor318 is also connected to an output terminal 330. The source terminal oftransistor 318 is connected to a resistor 320 and a capacitance 322. Theresistor 320 and the capacitance 322 are connected on the other side toground. The other side of the delay line 324 is connected to a 90° delayline 328 and a drain terminal of a transistor 326. The transistor 326represents a controllable electrical resistance element. The sourceterminal of transistor 326 is connected to ground. The gate terminal oftransistor 326 is connected to the source terminal of transistor 318.The other side of the delay line 328 is connected to the output terminal330.

The circuit of FIG. 22 uses a property of 90° transmission or delaylines 324 and 328 as an impedance inverter where, after the passing ofthe threshold power level in the B-class amplifier 318, the drain orcollector current appears and starts to grow and the voltage to drop,and the resistor 320 acting as a drain or collector current sensor isopening the transistor 326 as a controllable resistance element whichfinally provides a short circuit in the point of 90° line connectionwhich is the connection point between the 90° delay line 324 and the 90°delay line 328 and an open circuit on the opposite sides of the delaylines 324, 328. Thus, the RF-signal is switched from one branch toanother, providing constant input/output impedance of the predistortionunit circuit.

Another simplified configuration of the circuit of FIG. 22 is shown inFIG. 23. The circuit of FIG. 23 comprises an input terminal 340connected to a gate terminal of a transistor 342 and connected to adelay line 348. The transistor 342 is a B-class amplifier. The drainterminal of transistor 342 is connected to a power supply which is notshown and to an output terminal 354. The source terminal of transistor342 is connected to a resistor 344 acting as a drain or collectorcurrent sensor and a capacitance 346. The resistor 344 and thecapacitance 346 are connected to ground. The other side of the delayline 348 is connected to a delay line 350 and to a drain terminal of atransistor 352. The transistor 352 is a controllable electricalresistance element. The source terminal of the transistor 352 isconnected to ground. The gate terminal of transistor 352 is connected tothe source terminal of transistor 342.

FIG. 24 shows an embodiment of the present invention comprising an inputterminal connected to a resistor 362 and to a resistor 368. The otherside of the resistor 362 is connected to a capacitance 364. The otherside of the capacitance 364 is connected to a gate terminal of atransistor 366. The transistor 366 is a B-class amplifier. A biascontrol unit of threshold power 365 is connected to the gate terminal ofthe transistor 366. A power supply not shown is connected to a drainterminal of transistor 366. A source terminal of transistor 366 isconnected to ground. The drain terminal of transistor 366 is connectedto an output terminal 378. The other side of the resistor 368 isconnected to a capacitance 370. The other side of the capacitance 370 isconnected to a delay line 372. The other side of the delay line 372 isconnected to an adjustable capacitance 374 and to an input terminal ofthe amplifier 376. The capacitance 374 is used to control the AM/PMrate. The amplifier 376 is a gain control amplifier, allowing to adjustthe losses of the branch and isolation between the branches. Theamplifier 366 is used to control the AM/AM rate. The output terminal ofthe amplifier 376 is connected to the output terminal 378.

FIG. 25 shows another embodiment of the present invention. The circuitof FIG. 25 comprises an input terminal 380 connected to a capacitance382 and a capacitance 391. The capacitance 382 is connected on the otherside to a resistor 384. The resistor 384 is connected on the other sideto an input terminal of an amplifier 386. The amplifier 386 is a B-classamplifier. The output terminal of amplifier 386 is connected to anoutput terminal 398. The amplifier 386 is connected via a controlterminal to a resistor 390 and a capacitance 388. The resistor 390 andthe capacitance 388 are connected on the other side to ground. The otherside of the capacitance 391 is connected to a resistor 392. The otherside of the resistor 392 is connected to an input terminal of anamplifier 394. The amplifier 394 is a gain control amplifier. The outputterminal of the amplifier 394 is connected to a delay line 396. Thedelay line 396 is connected to the output terminal 398. A gain controlterminal of the amplifier 394 is connected to the resistor 390 and tothe capacitance 388.

FIG. 26 shows another embodiment of the present invention. Theembodiment comprises an input terminal 400 connected to a capacitance402 and a delay line 424. The capacitance 402 is connected to a resistor404. The other side of the resistor 404 is connected to a resistor 406,a capacitance 408, a gate terminal of a transistor 414 and a resistor416. The resistor 416 is connected on the other side to ground. Theresistor 406 is connected on the other side to a control voltage Vc. Thevoltage Vc controls the threshold voltage. The capacitance 408 isconnected to a resistor 410. The resistor 410 is connected on the otherside to an inductance 412 and to a drain terminal of the transistor 414.The inductance 412 is connected on the other side to the control voltageVc. The drain terminal of transistor 414 is connected to a capacitance418. The source terminal of transistor 414 is connected to a resistor420 and to a capacitance 422. The resistor 420 and the capacitance 422are connected on the other side to ground. The other side of the delayline 424 is connected to a capacitance 426. The other side of thecapacitance 426 is connected to the other side of the capacitance 418and to an output terminal 428. The transistor 414 is a B-classamplifier. The resistor 420 is used to control the AM and the PM rate.

The embodiment of FIG. 27 comprises an input terminal 430 connected to acapacitance 432 and to a resistor 458. The capacitance 432 is connectedto a resistor 434. The other side of the resistor 434 is connected to aresistor 436, a capacitance 438, a gate terminal of a transistor 448 anda resistor 450. The resistor 450 is connected on the other side toground. The resistor 436 is connected on the other side to a terminal444 which provides a threshold control signal. The capacitance 438 isconnected on the other side to a resistor 440. The resistor 440 isconnected on the other side to a resistor 442, a drain terminal oftransistor 448 and to a capacitance 452. The other side of the resistor442 is connected to a terminal 446 providing a supply voltage. The otherside of the capacitance 452 is connected to an output terminal 484. Asource terminal of transistor 448 is connected to a resistor 454 and toa capacitance 456. The other side of the resistor 454 and thecapacitance 456 is connected to ground. The other side of the resistor458 is connected to a capacitance 460 and to a resistance 462. The otherside of the capacitance 460 is connected to ground. The other side ofthe resistor 462 is connected to a resistor 464, a capacitance 466, agate terminal of a transistor 476, a resistor 478 and to a drainterminal of a transistor 480. The other side of the resistor 478 isconnected to ground. The other side of the resistor 464 is connected toa terminal 472. The terminal 472 provides a threshold control signal.The other side of the capacitance 466 is connected to a resistor 468.The resistor 468 is connected on the other side to a resistor 470, adrain terminal of the transistor 476 and to a capacitance 482. The otherside of the resistor 470 is connected to a terminal 474 providing asupply voltage. The source terminal of transistor 476 is connected toground. A source terminal of transistor 480 is connected to ground. Agate terminal of transistor 480 is connected to the resistor 454 and tothe capacitance 456. The other side of the capacitance 482 is connectedto the output terminal 484. The transistor 448 is a B-class amplifier.The resistor 454 is a drain current sensor. The transistor 476 is anA-class amplifier.

FIG. 28 shows a further alternative embodiment of the device 500 of theinvention. The device 500 is provided with an input terminal 501 and anoutput terminal 502, and with a power distributing circuit 510, a powercombining circuit 520, a linear branch 540 and non-linear branches 550,560. Each of the branches is provided with an input impedance 541, 551,561 and an output impedance 549, 559, 569, that have a value of forinstance 30 Ohm, 30 Ohm and 70 Ohm respectively. The second non-linearbranch 560 is provided with a delay line 581, that acts as a AM/PMcontrol. The non-linear branches 550, 560, the power distributingcircuit 510, and the power combining circuit 520 are all implemented, inthis specific embodiment as amplifiers including a transistor 512, 522,552, 562; a resistor 514, 524, 554, 564 connected to the output of thetransistor; a resistor 513, 523, 553, 563 connected to the input of thetransistor, and a feedback loop 515, 525, 555, 565. In the firstnon-linear brach 550 the resistor 554 is embedded as an adjustableimpedance, which is suitable for use as AM-AM control. The feedback 525in the power combining circuit and also those in the non-linear branches550, 560 are herin embodied as double negative feedback: a firstfeedback passes resistor 591 and capacitor 592; a second feedback passesthe control voltage input, and two resistors 593, 594. As the skilledperson will understand these feedbacks may be implemented differently.

As a consequence of the feedback loop 525, the input impedance of thepower combining circuit 520 is low. This, in combination with the outputimpedances 549, 559, 569 of the different branches assures that there isa goed isolation between the branches, and results in a high gain of theamplifier 522 in the combiner circuit 520. The complete circuit can berealized with amplifiers that may be discrete products or could beembedded in an integrated circuit.

The embodiments of the present invention provide an amplificationelement inside the parallel branch-circuits, which radically increasesthe AM/AM and AM/PM expansion rate and provides the isolation betweenthe said parallel branch-circuits outputs when combined, which helps forindependent tuning and adjustment of said parallel branch-circuitsparameters. The embodiments of the present invention also provide asolution for controlling the threshold power level, such asanti-parallel diodes with independent biasing and an A-class amplifier,or B/C-class amplifier with controlled bias in one independent nonlinearbranch-circuit, where the threshold level, the input power level, abovewhich the amplitude and phase transfer characteristics of thepredistortion unit start to be changed, can be adjusted by one controlbranched signal through one special port.

The embodiments of the present invention provide an additional port forthe threshold regulation; an amplifier, A- and B-Class, whichsignificantly improves AM/AM regulation rate, which is particularlyimportant for the multistage power amplifier compensation; introductionof more than one nonlinear branch-circuit; the embodiments of thepresent invention are not limited to the only microwave circuitry; thenon linear elements are not limited to just Shottky and PIN diodes, butinclude also other circuit elements such as transistors as a resistiveelement; and introduction of filters, for harmonic level control.

An ideal predistortion linearizer can be applied together with differentpower amplifiers; i.e. it need not to be adapted if one power amplifieris replaced by another power amplifier. The proposed solution to realizethis, is the use of a linearizer with at least two parallelbranch-circuits, at least one linear, the others nonlinear, thenonlinear branch-circuit comprising an impedance and an amplifier, thelinear branch-circuit comprising an impedance and optionally anamplifier. The nonlinear branch-circuit can be split into a plurality ofnonlinear branch-circuits.

The amplifier of the linearizer has the following functions. It isoperated as a diode, to block a reflection of the branched signal at apossible mismatch between the variable output resistance of the linearcircuit and the non-variable resistance of the switch thereafter;generating a harmonic signal that is opposed to the harmonic signal ofthe power amplifier; provision of a modification of the branched signalof certain traps within the power amplifier, which modification is inphase with the branched signal. Usually the branched signals aresomewhat out of phase, leading to a smoothing of the gain curve due tosaturation effects. This is particularly of importance if variousnonlinear circuits are provided. Due to the presence of the amplifier inthe linearizer, the circuits can be adapted independently of each other.The use of amplifiers is furthermore advantageous, since they can beintegrated easily (instead of the diodes), therewith reducing the amountof assembly. The parallel placements of the circuits has the functionthat phase and amplitude are separated.

The linearizer cancels more than 20 dB of the third-orderintermodulation. This third-order intermodulation is very important forwider bands, such as wideband CDMA and EDGE. The linearizer is verysuitable for use in combination with a multistage power amplifier. Thelinearizer can be used for a variety of power amplifiers due torelatively independent adjustability of the three key parameters such asAM/AM, AM/PM and threshold power.

New characteristics and advantages of the invention covered by thisdocument have been set forth in the foregoing description. It will beunderstood, however, that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of parts, without exceeding the scope ofthe invention. The scope of the invention is, of course, defined in thelanguage in which the appended claims are expressed.

1. A method for a predistortion linearization of a branched signal for aRF amplifier, comprising: supplying an input signal to at least oneinput terminal (2); distributing the input signal present on at leastone input terminal (2) to a plurality of parallel branch-circuits (16,18, 20) as branched signals by a power distributing circuit (4);controlling a phase parameter and/or an amplitude parameter of thebranched signals by at least one nonlinear branch-circuit (18, 20);controlling a phase parameter and an amplitude parameter of the branchedsignals by at least one linear branch-circuit (16); combining outputsignals of at least one nonlinear branch circuit (18, 20) with theoutput signals of at least one linear branch circuit (16) by a powercombining circuit (12); providing an final output signal of thepredistortion unit from the power combining circuit (12) on at least oneoutput terminal (14).
 2. The method of claim 1, wherein the controllingof a phase parameter and/or an amplitude parameter of the branchedsignal by at least one nonlinear branch-circuit (18, 20) comprises:controlling a phase of a branched signal by at least one phase controlunit (6) and/or; controlling an amplitude of a branched signal by atleast one linear amplitude control unit (8) and/or; controlling anamplitude of a branched signal by at least one nonlinear amplitudecontrol unit (10).
 3. The method of claim 1, wherein the controlling ofa phase parameter and/or an amplitude parameter of a branched signal byat least one linear branch-circuit (16) comprises: controlling a phasevariation of a branched signal by at least one phase control unit (6)and/or; controlling an amplitude of a branched signal by at least onelinear amplitude control unit (8).
 4. The method of claim 2, wherein thelinear amplitude control unit (8) and/or the nonlinear amplitude controlunit (10) are/is controlled depending on a power level of an inputsignal.
 5. The method of claim 2, wherein the linear (8) amplitudecontrol unit and/or the nonlinear amplitude control unit (10) are/iscontrolled depending on an external adjustable value.
 6. The method ofclaim 1, wherein the linear (16) amplitude control unit and/or thenonlinear branch-circuit (18, 20) have their/its own specific RF powerlevel from which their/its predistortion of amplitude and/or phasestarts, which is defined by an individual nonlinear function.
 7. Amethod for a predistortion linearization, in particular compensation oftemperature of a linearized power module, where a varicap is acontrolled element of an AM/AM compensation loop and an amplifiercontrol element for AM/PM compensation, comprising: supplying an inputsignal to at least one input terminal (2); distributing the input signalpresent on at least one input terminal (2) to a plurality of parallelbranch-circuits (16, 18, 20) as branched signals by a power distributingcircuit; controlling a phase parameter and/or an amplitude parameter ofthe branched signals by at least one nonlinear branch-circuit (18, 20);controlling a phase parameter and/or an amplitude parameter of thebranched signals by at least one linear branch-circuit (16); combiningthe output signal of at least one nonlinear branch circuit (18, 20) withthe output signal of at least one linear branch circuit (16) by a powercombining circuit (12); providing a final output signal of thepredistortion unit from the power combining circuit (12) on at least oneoutput terminal (14).
 8. An electronic device comprising a circuit for apredistortion unit linearizing a signal for a RF amplifier, comprising:at least one input terminal (2) supplying an input signal; a powerdistributing circuit (4) distributing the input signal present on atleast one input terminal (2) to a plurality of parallel branch-circuits(16, 18, 20) as branched signals; at least one nonlinear branch-circuit(18, 20) controlling a phase parameter and/or an amplitude parameter ofthe branched signals; at least one linear branch-circuit (16)controlling a phase parameter and/or an amplitude parameter of thebranched signals; a power combining circuit (12) combining outputsignals of at least one nonlinear branch circuit (18, 20) with theoutput signals of at least one linear branch circuit (16); at least oneoutput terminal (14) providing an output signal of the predistortionunit from the power combining circuit (12).
 9. The device of claim 8,wherein the nonlinear branch-circuit (18, 20) comprises: at least onephase control unit (6) controlling the phase of a branched signaland/or; at least one linear amplitude control unit (8) controlling theamplitude of a branched signal and/or; at least one nonlinear amplitudecontrol unit (10) controlling the amplitude of a branched signal. 10.The device of claim 8, wherein the linear branch-circuit (16) comprises:at least one phase control unit (6) controlling the phase of a branchedsignal and/or; at least one linear amplitude control unit (8)controlling the amplitude of a branched signal.
 11. The device of claim9, wherein the nonlinear amplitude control unit (10) comprises at leastone nonlinear element and at least one amplifier.
 12. The device ofclaim 10, wherein the linear amplitude control unit (8) is a gaincontrol amplifier (280) and/or an attenuator and/or a resistor and/or adissipative transmission line and/or a controllable resistive component.13. The device of claim 8, wherein the linear (16) and/or the nonlinearbranch-circuit (18, 20) have a filtering circuit at an output terminal.14. The device of claim 8, wherein the phase control unit comprises atleast one transmission line (204) or at least one controlled resistiveelement (326).
 15. The device of claim 8, wherein the circuit isintegrated with a semiconductor device.